EarCut is failing in some cases

[gkjohnson]

Is this because there are crossing edges in a single loop?

[gkjohnson]

Seems likely to be due to edge crossings:

https://jsfiddle.net/4mfn09up/5/

[gkjohnson]

Though on failing cases for the rover model there are no crossings listed.

Edit: Though there could still be crossings between paths

Edit2: Nope still no crossings

Count Code for All Loops

export function countCrossings( loops ) {

	const l0 = new Line3();
	const l1 = new Line3();
	let tot = 0;

	for ( let k = 0, kl = loops.length; k < kl; k ++ ) {

		const points0 = loops[ k ];
		for ( let i = 0, l = points0.length; i < l; i ++ ) {

			const i1 = ( i + 1 ) % l;
			l0.start.copy( points0[ i ] );
			l0.end.copy( points0[ i1 ] );

			l0.start.z = 0;
			l0.end.z = 0;

			for ( let k2 = k; k2 < kl; k2 ++ ) {

				const points1 = loops[ k2 ];
				for ( let j = 0, jl = points1.length; j < jl; j ++ ) {

					if ( k === k2 && j < i ) {

						continue;

					}

					const j1 = ( j + 1 ) % jl;
					l1.start.copy( points1[ j ] );
					l1.end.copy( points1[ j1 ] );

					l1.start.z = 0;
					l1.end.z = 0;

					if (
						l1.start.equals( l0.start ) ||
						l1.end.equals( l0.end ) ||
						l1.start.equals( l0.end ) ||
						l1.end.equals( l0.start )
					) {

						continue;

					}

					if ( lineCrossesLine( l0, l1 ) ) {

						tot ++;

					}

				}

			}

		}

	}

	return tot;

}

Crossing Count Code

function countCrossings( points ) {

	const l0 = new Line3();
	const l1 = new Line3();
	let tot = 0;

	for ( let i = 0, l = points.length; i < l; i ++ ) {

		const i1 = ( i + 1 ) % l;
		l0.start.copy( points[ i ] );
		l0.end.copy( points[ i1 ] );

		l0.start.z = 0;
		l0.end.z = 0;

		for ( let j = i + 2; j < l; j ++ ) {

			const j1 = ( j + 1 ) % l;
			l1.start.copy( points[ j ] );
			l1.end.copy( points[ j1 ] );

			l1.start.z = 0;
			l1.end.z = 0;

			if (
				l1.start.equals( l0.start ) ||
				l1.end.equals( l0.end ) ||
				l1.start.equals( l0.end ) ||
				l1.end.equals( l0.start )

			) {

				continue;

			}

			if ( lineCrossesLine( l0, l1 ) ) {

				tot ++;

			}

		}

	}

	return tot;

}

[gkjohnson]

mapbox/earcut#163

[gkjohnson]

It looks like having points that are in the same spot - either within the same loop or between holes - can cause issues. Would be best to figure out how to remove those cases.

Maybe inflation will help?

[gkjohnson]

Consider using the cdt2d package rather than three.js' earcut.

[gkjohnson]

Other alternatives:

• poly2tri
• pnltri
• libtess.js
• Constrainautor